Substituted pyrazoles



United States Patent 1 2,833,779 SUBSTITUTED PYRAZOLES Thomas L. Fields, Pearl River, N. Y., and Martin J.

Weiss, Oradell, and William B. Wright, Jr., Wood'clilf.

Lake, N. 1., assignors to American Cyanamid Company, New York,- N. Y., a corporation of Maine No Drawing. Application October 29, 1956 Serial No. 618,691 12 Claims. (Cl.'260296) in which R is a halogen, hydroxy, or an alkoxy radical,

R is hydrogen or a halogen, lower alkoxy, oralkyl radical, and R and R are lower alkyl or pyridyl radicals, one of which is a pyridyl radical and the other is a lower alkyl radical. For. example, the various radicals attached to the nitrogen in the (1) position on the pyrazole ring can be chlorophenyl, bromophenyl, 'dichlorophenyl, dibromophenyl, chloromethoxyphenyl, chloroethoxyphenyl, bromomethoxyphenyl, bromoethox'yphenyl, chlorornethylphenyl, chloroethylphenyl, bromomethylphenyl, bromoethylphenyl, methoxyphenyl, hydroxyphenyl, etc. v

The compounds of the present invention are generally solids, although some are oils. They are relatively more soluble in organic solvents, such as ethanol, acetone, ethyl acetate, benzene, or chloroform, than in water. In the form of their salts, they are water soluble in varying extent. The salts are ordinarily crystallizable from alcohol and are insoluble in ether, benzene, chloroform, and

the like.

' The present compounds are preferably prepared by reacting a pyridylbeta-dicarbonyl compound with a monosubstituted hydrazine. The reaction which takes place can be illustrated by the following equation:

' :parts of ethanol is heated at reflux for five hours and then drug.

ice

As shown above, the R substituent can be in the 3- or 5- position on the pyrazole ring, which is also true of the pyridyl substituent, dependingon the, manner in which the ring'is condensed.

The process of the present'invention can be carried out under acidic, neutral, or basic conditions in aqueous solution. It can also be carried out in solvents such as ethanol, methanol, propanol, benzene, toluene,etc. The temperature within whichthe reaction may be carried out will vary from about 20 C. to, about 200 C.

In carrying outthe reaction, the two reactants are dissolved together in asolvent such as ethanoland the solution is warmed to a temperature of from about to C. for-a period of from one to 20 hours. After cooling the reaction mixture, the product may crystallize or may be distilled. As an vaid to crystallization, it sometimes is desirable that the reaction mixture be concentrated and then cooled. .The use of acid has a catalyzing effect, and the desired product is obtained as the.

crystalline, acid addition salt:

The present; process can be carried out in two steps, wherein the beta-dicarbonyl compound is reacted with a monosubstituted hydrazine to. produce an intermediate hydrazone. Theintermediate is then cyclized by heating, preferably in the presence of acid, which catalyzes the reaction.

1 The compounds of the :present invention have been found to have analgesic; activity when tested by the method describedin J. Pharm. Exptl. Therap. 80, 300-307, andmodified in J. Pharmacol. Exptl. Therap. 98, 121137. The activity in many instances was found to be equal to that of Demer'ol, a-syn-thetic, clinically useful analgesic .This potency is markedly {superior to that of mild analgesic drugs such as aspirin. The present compounds,'therefore,:are usefuliin the relief-of pain. They can be given in the form of,pills,.tablets, powders, liquids,

and other well-knownmethods 'of administering drugs. The. following examples illustrate the preparation of compounds of th e'ipresentinvention.

EXAM LE 1 1 (p chlorophenyl) 3(.and -5)-methyl-5(and 3)-(4 g I pyridyl) -pyraz0les A mixture of 16.4 'parts of'isonicotinoylacetone, 17.9 parts of p-chlorophenylhydrazine hydrochloride, 4.8 parts by volume of 4.2 N alcoholic hydrogen chloride, and

cooled;v Theaprecipitate isafiltered off and then recrystallized ,from' ethanol. .The. crystalline. product is converted to-the base.bytreatment.with dilute ammonium ,hydroxide-andthel base isfrecrystallized from hexane. Isomerlmelts at 903-91? C. H v

" Patented- May 6, 1958- The ethanolic filtrate from the first filtration is 'concentrated to dryness and the residueis treated with dilute ammonium hydroxide. The insoluble portion is recrystallized from hexane until pure isomer II, melting point 117-1,18 IC.1=;;= pg} i f ExAMPLE 2; A

A mixture of 16.4 partsof isonicotinoyl-aceton'e;14.3 parts of m-chlorophenylhydrazine, 28.8 parts by volume of 4.2 N alcoholic hydrogen chloride, and 160 parts of ethanol is refluxed for five hours and then concentrated to about 50 parts by volume. On cooling, a precipitate separates and is filtered off. Recrystallization from ethanol yields pure isomerI as the hydrochloride, melting point 238 242 c. v 1 i u The alcoholifiltratefrom the first'filtrationis concentrateduntil the'solventis removed andiis then triturated with ether! The precipitate which separates is filtered off and treated with aqueous ammonium hydroxide. The white crystals are separated and recrystallized from hexane. The pure isomer II base melts at 75 76 C. When treated with alcoholic "hydrogen chloride, isomer II hydrochloride, melting point 208 210} C., is obtained. 3 p I e j EXAMPLE3 s 1- (2,4-dichlorophenyl) -3 (and 5 )-methyl-5 (and 3) -(4-pyrl idyl)-pyrdzoIes A mixture of 16.4 parts of isonicotinoylacetone,121.4 parts of 2,4-dichlorophenylhydrazine :hydrochloride, and 80 parts of ethanol is refluxed for seven hours and then cooled. The precipitate is filtered ofl and recrystallized from ethanol. The product, isomer I hydrochloride, melts at 244-249 C. When this material is 'treated with aqueous ammonia, isomer I free base is obtained, melting point 13l3l34 C.

The ethanolic filtrate from the'first filtration is concentrated "to dryness and t the residue is treated with aqueous ammonia. The precipitate is separated and recrystallized from ethanol until pure isomer II free base is obtained, melting point 135-136 C.

The melting point of the mixture of the two bases is 105-115,,,C.

EXAMPLE 4 These'products are prepared by reacting isonicotinoyl-v chloride. Isomer I free .base melts at 158-159 C..

Isomer II free base melts at 140-l41 C. A mixture of the free bases melts at 118"123 C.

EXAMPLE 5 1-(3-chloro-2-methylphenyl)-3(and 5)-methyl-5 (and 3)- -Py i yl) -pyrazoles A mixture of 16.4 parts of isonicotinoylacetone, 19.4

, parts of 3-chloro-2-methylphenylhydrazine hydrochloride;

and 80 parts of ethanol is refluxed for seven hours. The reaction mixture is concentrated to a syrup, triturated with ether and then filtered. The solid is recrystallized from 60 parts of ethanol. A second recrystallization yields pure isomer I hydrochloride, melting point 284- 290 C.

4 EXAMPLE 6 pyrazole hydrochloride and free base A mixture of 23.5 parts of p-bromophenylhydrazine hydrochloride, 16.4 parts of isonicotinoylacetone, and parts of ethanol is refluxed for two-seven hours and cooled. The precipitate which separates is filtered and recrystallized from ethanol. The yield of the hydrochloride, melting point 249-253 C., is 47%. When the hydrochloride is treated with aqueous ammonia, the free base, melting point 124-126 C., is obtained.

EXAMPLE 7 J o-chlorophenyl) -3 (or 5 )-methyl-5 (or 3)-(4-pyridyl)- pyrazole hydrochloride and free base EXAMPLE 8 1- (4-chloro-2-methylphenyl) -3 (or 5 -methyl-5 (or 3) (4-pyridyl) -pyrazole hydrochloride This compound is obtained by the method described in Example 6, except that 4-chloro-2-methylphenylhydrazine hydrochloride is used in place of p-bromophenylhydrazine hydrochloride and the final reaction mixture is concentrated before the hydrochloride is separated. The hydrochloride melts at 218-225 C.

EXAMPLE 9 1-(2,5-dichlorophenyl) -3 (or 5 -methyl-5 (or 3 )-(4- pyridyl) -pyrazole and hydrochloride 1 A mixture of 18.6 parts of 2,5-dichlorophenylhydrazine, 16.4 parts of isonicotinoylacetone and'SO parts of ethanol is refluxed for five hours and cooled and then filtered. The yield of product which melts at 132-l34 C. is 43%. The hydrochloride, melting point 246-249 C. is obtained when the base is treated with alcoho1ic.hydrogen chloride. T

EXAMPLE 10 I p-chlorophenyl) -3( or 5 )-methyl-5 (or 3 )-(2-pyridyl)- pyrazole and hydrochloride These products are obtained by the same methods as described in Example 9, except that p-chlorophenylhydrazine is used in place of 2,5-dichlorophenylhydrazine and picolinoylacetone is used in place of isonicotinoylacetone. The yield of base, melting point 9496 C., is 74%. The hydrochloride melts at 187- l89 C.

EXAMPLE ll A mixture of 4.9 parts of nicotinoyl acetone, 4.3 parts of p-chlorophenylhydrazine and 25 parts of ethanol is Crude isomer II hydrochloride is obtained when the filtrate from the first ethanol recrystallization is concentrated. Recrystallization twice from ethanol results in pure isomer II hydrochloride, melting point 213-21S C.

allowed to stand for 24 hours. One molar equivalent of ethanolic hydrogen chloride is added and the reaction -mixture is heated at reflux for four hours and then cooled. Crystals separate and are recrystallized from ethanol. The pure hydrochloride is obtained in 50% yield and melts at 220-223 C.

EXAMPLE l2 I m-chlorophenyl) -3 (or 5) -methyl-5(0r 3 (3-pyridyl) pyrazole hydrochloride allowed to stand for ten hours at room temperature and 5 a is then refluxed for sixtwenty hours. The reactiorimixture is distilled and the portion boiling at 1565-162 C. (0.2 mm.) is collected. The yield is 52%. When this material is treated with alcoholic hydrogen chloride, the hydrochloride, melting point 170-172 C., is obtained.

EXAMPLE 13 1(m-chl0r0phenyl) -3 (or 5 -methyl-5 (or 3 -(2-pyridyl) pyrazole hydrochloride This compound is prepared by the method described in Example 12, except that picolinoylacetone is substituted for nicotinoylacetone. The yield of base, boiling point l70l73' C. (0.8 mm.), is 85%. The hydrochloride melts at l54-l56 C.

EXAMPLE 14 (m-chlorophenyl) -3 (r )-ethyl-5 (or 3 (4-pyridy'l) pyrazole hydrochloride This compound is prepared by the method described in Example 12, except that 1-(4-pyridyl)-l,3-pentanedione is substituted for the nicotinoylacetone. The yield of base, boiling point 166"170 C. (0.3 mm.), is 78%. The hydrochloride melts at 207-209 C.

EXAMPLE 15 1-(p-chl0r0phenyl)-3 (0r 5 -ethyl-5 (0r 3 -(4-pyridyl) pyrazole hydrochloride This compound is prepared by the method described in Example 14, except that p-chlorophenylhydrazine is used in place of m-chlorophenylhydrazine. The yield of base, boiling point 182186 C. (0.8 mm.), is 70%. The hydrochloride melts at 229-232 C.

EXAMPLE :16

1-(m-methoxyphenyl)-3(0r 5)-methyl-5(0r 3)-(3- pyridyl)-pyrazole This compound is prepared by the method described in Example 12, except that m-methoxyphenylhydrazine is used in place of the m-chlorophenylhydrazine. The yield of product, boiling point 165170 C. (0.5 mm.), is 72%.

EXAMPLE 17 1 m-methoxyphenyl -3 or 5) -methyl-5 (or 3) -(4- pyridyl -pyraz0le A mixture of 16.4 parts of isonicotinoylacetone, 13.8 parts of m-methoxyphenylhydrazine, and 240 parts of ethanol is refluxed for ten hours and then distilled. The yield of product, boiling point l70180 C. (1 mm.), is 72%.

EXAMPLE 18 1(m-hydr0xyphenyl)-3(0r 5)-mezhyl-5 (0r 3)-(4- pyridyl)-pyrazole hydrobromide and in which R is a member of the group consisting of halogen, hydroxyl, and lower alkoxy radicals, R is a member of the group consisting of hydrogen, halogen, lower alkyl, and lower alkoxy radicals, and R is a lower alkyl radical and acid addition salts thereof.

2 The compound l-(m-chlorophenyl)-3-methyl-5-(3 pyridyl)-pyrazole.

3. The compound l-(m-chlorophenyl)-5-methyl-3(3- pyridyl) -pyrazole.

4. The compound l-(m-chlorophenyl)-3-methyl-5-(4- pyridyl -pyrazole.

5. The compound l-(m-chlorophenyl)-5-methyl-3-(4- pyridyl -pyrazo1e.

6. The compound l-(p-chlorophenyl)-3-methyl-5 (4- pyridyl -pyrazole.

7. A method of preparing a compound selected from the group having the general formulas:

and

in which R is a member of the group consisting of halogen, hydroxyl, and lower alkoxy radicals, R is a member of the group consisting of hydrogen, halogen, lower alkyl, and lower alkoxy radicals, and R is a lower alkyl radical which comprises reacting a pyridyl beta-dicarbonyl com pound having the formula:

0 H I -CHz-O-R:

in which R is as previously defined with a hydrazine compound having the formula:

Ham-1Q in which R and R are as defined above.

8. A method of preparing l-(m-chlorophenyl)-3-methyl-5-(3-pyridyl) -pyrazole which comprises reacting nicotinoylacetone with m-chlorophenylhydrazine and recovering said product therefrom.

9. A method of preparing 1-(m-chlorophenyD-S-methyl-3-(3-pyridyl)-pyrazole which comprises reacting nicotinoylacetone with m-chlorophenylhydrazine ering said product therefrom.

10. A method of preparing 1-(m-chlorophenyl)-3- methy1-5-(4-pyridyl)-pyrazole which comprises reacting isonicotinoylacetone with m-chlorophenylhydrazine and recovering said product therefrom.

11. A method of preparing l-(m-chlorophenyD-S- methyl-3-(4-pyridyl)-pyrazole which comprises reacting and recovrecovering said product therefrom.

12. A method of preparing 1-(p-ch1oropheny1)-3-' methyl-5-(4-pyridyl)-pyrazo1e which comprises reacting isonicotinoylacetone with p-chlorophenylhydrazine and recovering said product therefrom.

References Cited in the file of this patent Davis: Chem. Abstracts, vol. 35, col. 5501 (1941). Treibs et a1.: Chem. Abstracts, vol. 47, cols. 3295-6 (1953). 

1. A COMPOUND SELECTED FROM THE GROUP CONSISTING OF THOSE HAVING THE GENERAL FORMULAS: 